Optical device

ABSTRACT

An optical device is disclose herein. In some embodiments, an optical device includes an active liquid crystal element film, wherein the active liquid crystal element film comprises two base films, an active liquid crystal layer present between the two base films, wherein the active liquid crystal layer contains a liquid crystal compound and is capable of switching between a first oriented state and a second oriented state, and a polarizing coating layer, wherein the polarizing coating layer is present between one of the two base films and the active liquid crystal layer. The optical device is capable of varying transmittance, and can be used for various applications such as sunglasses, AR (augmented reality) or VR (virtual reality) eyewear, an outer wall of a building or a sunroof for a vehicle.

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/KR2018/004785, filed on Apr. 25,2018, claims priority from Korean Patent Application No.10-2017-0053018, filed on Apr. 25, 2017, the disclosures of which areincorporated by reference herein.

TECHNICAL FIELD Technical Field

The present application relates to an optical device.

BACKGROUND ART

Various optical devices are known, which are designed so thattransmittance can be varied using liquid crystal compounds.

For example, variable transmittance devices using a so-called GH cell(guest host cell), to which a mixture of a host material and a dichroicdye guest is applied, are known.

Such variable transmittance devices are applied to various applicationsincluding eyewear such as sunglasses and eyeglasses, outward walls of abuilding or sunroofs of a vehicle, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically showing a cross-section of the activeliquid crystal element film having a folded film shape in accordancewith an embodiment of the present disclosure.

FIG. 2 is a diagram schematically showing a cross-section of the activeliquid crystal element film having a folded film shape in accordancewith an embodiment of the present disclosure.

FIG. 3 is diagram schematically showing a top view of a liquid crystalelement film in accordance with an embodiment of the present disclosure.

FIGS. 4 to 8 depict optical devices in accordance with embodiments ofthe present disclosure.

DISCLOSURE Technical Problem

The present application provides an optical device.

Technical Solution

The present application is an optical device capable of adjustingtransmittance, which relates to, for example, an optical device capableof switching at least between a transparent mode and a black mode.

The transparent mode is a state where the optical device exhibits arelatively high transmittance, and the black mode is a state where theoptical device exhibits a relatively low transmittance.

In one example, the optical device may have a transmittance in thetransparent mode of about 15% or more, about 20% or more, about 25% ormore, about 30% or more, about 35% or more, about 40% or more, about 45%or more, or about 50% or more. Also, the optical device may have atransmittance in the black mode of about 20% or less, about 15% or less,about 10% or less, about 5% or less, about 3% or less, about 1% or less,or about 0.8% or less or so.

The higher the transmittance in the transparent mode is, the moreadvantageous it is, and the lower the transmittance in the black modeis, the more advantageous it is, so that each of the upper limit and thelower limit is not particularly limited. In one example, the upper limitof the transmittance in the transparent mode may be about 100%, about95%, about 90%, about 85%, about 80%, about 75%, about 70%, about 65%,about 60%, about 55%, about 50%, about 45%, about 40%, about 35%, about30%, or about 25% or so. The lower limit of the transmittance in theblack mode may be about 0%, about 0.5%, about 1%, about 2%, about 3%,about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, or about 10%or so.

The transmittance may be a linear light transmittance. The term linearlight transmittance may be a ratio of, relative to light which isincident on the optical device in a predetermined direction, light(linear light) transmitted through the optical device in the samedirection as the incident direction. In one example, the transmittancemay be a result of measurement (normal light transmittance) with respectto light incident in a direction parallel to the surface normal of theoptical device.

In the optical device of the present application, the light whosetransmittance is controlled may be UV-A region ultraviolet light,visible light or near-infrared light. According to a commonly useddefinition, the UV-A region ultraviolet light is used to mean radiationhaving a wavelength in a range of 320 nm to 380 nm, the visible light isused to mean radiation having a wavelength in a range of 380 nm to 780nm and the near-infrared light is used to mean radiation having awavelength in a range of 780 nm to 2000 nm.

The optical device of the present application is designed to be capableof switching at least between the transparent mode and the black mode.If desired, the optical device may also be designed to be capable ofimplementing, for example, a third mode which may represent anytransmittance between the transmittance of the transparent mode and thetransmittance of the black mode.

The switching between such modes can be achieved, as the optical devicecomprises an active liquid crystal element film. Here, the active liquidcrystal element film is a liquid crystal element capable of switchingbetween at least two or more oriented states of light axes, for example,first and second oriented states. Here, the optical axis may mean thelong axis direction when the liquid crystal compound included in theliquid crystal element is a rod type, and may mean the normal directionof the disc plane when it is a discotic type. For example, in the casewhere the liquid crystal element comprises a plurality of liquid crystalcompounds whose directions of the optical axes are different from eachother in any oriented state, the optical axis of the liquid crystalelement may be defined as an average optical axis, and in this case, theaverage optical axis may mean the vector sum of the optical axes of theliquid crystal compounds.

The oriented state in such a liquid crystal element can be changed byapplying energy, for example, by applying a voltage. For example, theliquid crystal element may have any one of the first and second orientedstates in a state without voltage application, and may be switched toanother oriented state when a voltage is applied.

The black mode may be implemented in any one of the first and secondoriented states, and the transparent mode may be implemented in anotheroriented state. For convenience, it is described herein that the blackmode is implemented in the first state.

The liquid crystal element film may comprise a liquid crystal layercontaining at least a liquid crystal compound. In one example, theliquid crystal layer is a so-called guest host liquid crystal layer,which may be a liquid crystal layer comprising a liquid crystal compoundand an anisotropic dye.

The liquid crystal layer is a liquid crystal layer using a so-calledguest host effect, which may be a liquid crystal layer in which theanisotropic dyes are aligned according to a alignment direction of theliquid crystal compound (hereinafter, may be referred to as a liquidcrystal host). The alignment direction of the liquid crystal host may beadjusted depending on whether or not external energy is applied.

The type of the liquid crystal host used in the liquid crystal layer isnot particularly limited, and a general type of liquid crystal compoundapplied to realize the guest host effect may be used.

For example, as the liquid crystal host, a smectic liquid crystalcompound, a nematic liquid crystal compound, or a cholesteric liquidcrystal compound may be used. In general, a nematic liquid crystalcompound may be used. The nematic liquid crystal compound may be in arod form or may be in a discotic form.

As such a nematic liquid crystal compound, one having a clearing pointof, for example, about 40° C. or more, about 50° C. or more, about 60°C. or more, about 70° C. or more, about 80° C. or more, about 90° C. ormore, about 100° C. or more, or about 110° C. or more, or having a phasetransition point in the above range, that is, a phase transition pointto an isotropic phase on a nematic phase, can be selected. In oneexample, the clearing point or phase transition point may be about 160°C. or less, about 150° C. or less, or about 140° C. or less.

The liquid crystal compound may have dielectric constant anisotropy of anegative number or a positive number. The absolute value of thedielectric constant anisotropy can be appropriately selected inconsideration of the object. For example, the dielectric constantanisotropy may be more than 3 or more than 7, or may be less than −2 orless than −3.

The liquid crystal compound may also have optical anisotropy (Δn) ofabout 0.01 or more, or about 0.04 or more. In another example, theoptical anisotropy of the liquid crystal compound may be about 0.3 orless, or about 0.27 or less.

Liquid crystal compounds that can be used as the liquid crystal host ofthe guest host liquid crystal layer are well known to those skilled inthe art, whereby the liquid crystal compound can be freely selected fromthem.

The liquid crystal layer comprises an anisotropic dye together with theliquid crystal host. The term “dye” may mean a material capable ofintensively absorbing and/or modifying light in at least a part or theentire range in a visible light region, for example, a wavelength rangeof 380 nm to 780 nm, and the term “anisotropic dye” may mean a materialcapable of anisotropically absorbing light in at least a part or theentire range of the visible light region.

As the anisotropic dye, for example, known dyes known to have propertiesthat can be aligned according to the aligned state of the liquid crystalhost may be selected and used. For example, azo dyes or anthraquinonedyes and the like may be used as the anisotropic dyes, and the liquidcrystal layer may also comprise one or two or more dyes in order toachieve light absorption in a wide wavelength range.

A dichroic ratio of the anisotropic dye can be appropriately selected inconsideration of the object. For example, the anisotropic dye may have adichroic ratio of 5 or more to 20 or less. For example, in the case of ap-type dye, the term “dichroic ratio” may mean a value obtained bydividing absorption of polarized light parallel to the long axisdirection of the dye by absorption of polarized light parallel to thedirection perpendicular to the long axis direction. The anisotropic dyemay have the dichroic ratio in at least a part of wavelengths or any onewavelength or the entire range in the wavelength range of the visiblelight region, for example, in the wavelength range of about 380 nm to780 nm or about 400 nm to 700 nm.

The content of the anisotropic dye in the liquid crystal layer may beappropriately selected in consideration of the object. For example, thecontent of the anisotropic dye may be selected in a range of 0.1 to 10%by weight based on the total weight of the liquid crystal host and theanisotropic dye. The ratio of the anisotropic dye may be changed inconsideration of the desired transmittance and the solubility of theanisotropic dye in the liquid crystal host, and the like.

The liquid crystal layer basically comprises the liquid crystal host andthe anisotropic dye, and may further comprise other optional additivesaccording to a known form, if necessary. As an example of the additive,a chiral dopant or a stabilizer can be exemplified, without beinglimited thereto.

The liquid crystal layer may have an anisotropy degree (R) of about 0.5or more. The anisotropy degree (R) is determined from absorbance (E(p))of a light beam polarized parallel to the alignment direction of theliquid crystal host and absorbance (E(s)) of a light beam polarizedperpendicularly to the alignment direction of the liquid crystal hostaccording to the following equation.

<Anisotropy Degree Equation>

Anisotropy degree (R)=[E(p)−E(s)]/[E(p)+2*E(s)]

The above-used reference is another identical apparatus that does notcontain a dye in the liquid crystal layer.

Specifically, the anisotropy degree (R) may be determined from the value(E(p)) for the absorbance of the liquid crystal layer in which the dyemolecules are horizontally oriented and the value (E(s)) for theabsorbance of the same liquid crystal layer in which the dye moleculesare vertically oriented. The absorbance is measured in comparison with aliquid crystal layer which does not contain any dye at all but has thesame constitution. This measurement may be performed, in the case of onevibration plane, using a polarized beam vibrating in a directionparallel to the alignment direction (E(p)) and vibrating in a directionperpendicular to the alignment direction (E(s)) in subsequentmeasurements. The liquid crystal layer is not switched or rotated duringthe measurement, and thus the measurement of E(p) and E(s) may beperformed by rotating the vibration plane of the polarized incidentlight.

One example of a detailed procedure is as described below. The spectrafor the measurement of E(p) and E(s) can be recorded using aspectrometer such as a Perkin Elmer Lambda 1050 UV spectrometer. Thespectrometer is equipped with Glan-Thompson polarizers for a wavelengthrange of 250 nm to 2500 nm in both of the measuring beam and thereference beam. The two polarizers are controlled by a stepping motorand are oriented in the same direction. The change in the polarizerdirection of the polarizer, for example, the conversion of 0 degrees to90 degrees, is always performed synchronously and in the same directionwith respect to the measuring beam and the reference beam. Theorientation of the individual polarizers may be measured using themethod described in T. Karstens' 1973 thesis in the University ofWurzburg.

In this method, the polarizer is rotated stepwise by 5 degrees withrespect to the oriented dichroic sample, and the absorbance is recorded,for example, at a fixed wavelength in the maximum absorption region. Anew zero line is executed for each polarizer position. For themeasurement of two dichroic spectra E(p) and E(s), anti-parallel-rubbedtest cells coated with polyimide AL-1054 from JSR are located in boththe measuring beam and the reference beam. Two test cells can beselected with the same layer thickness. The test cell containing a purehost (liquid crystal compound) is placed in the reference beam. The testcell containing a solution of a dye in the liquid crystals is placed inthe measuring beam. Two test cells for the measuring beam and thereference beam are installed in a ray path in the same alignmentdirection. In order to ensure the maximum possible accuracy of thespectrometer, E(p) may be in its maximum absorption wavelength range,for example, a wavelength range of 0.5 to 1.5. This corresponds totransmittance of 30% to 5%. This is set by correspondingly adjusting thelayer thickness and/or the dye concentration.

The anisotropy degree (R) can be calculated from the measured values ofE(p) and E(s) according to the above equation as shown in a reference[see: “Polarized Light in Optics and Spectroscopy,” D. S. Kliger et al.,Academic Press, 1990].

In another example, the anisotropy degree (R) may be about 0.55 or more,0.6 or more, or 0.65 or more. The anisotropy degree (R) may be, forexample, about 0.9 or less, about 0.85 or less, about 0.8 or less, about0.75 or less, or about 0.7 or less.

Such an anisotropy degree (R) can be achieved by controlling the kind ofthe liquid crystal layer, for example, the kind of the liquid crystalcompound (host), the kind and the ratio of the anisotropic dye, or thethickness of the liquid crystal layer, and the like.

It is possible to provide an optical device with high contrast ratio byincreasing the difference in the transmittance between the transparentstate and the black state while using lower energy through theanisotropy degree (R) in the above range.

The thickness of the liquid crystal layer may be appropriately selectedin consideration of the object, for example, the desired anisotropydegree or the like. In one example, the thickness of the liquid crystallayer may be about 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.5μm or more, 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more,3 μm or more, 3.5 μm or more, 4 μm or more, 4.5 μm or more, 5 μm ormore, 5.5 μm or more, 6 μm or more, 6.5 μm or more, 7 μm or more, 7.5 μmor more, 8 μm or more, 8.5 μm or more, 9 μm or more, or 9.5 μm or more.By controlling the thickness in this manner, it is possible to realizean optical device having a large difference in transmittance between thetransparent state and the black state, that is, a device having a largecontrast ratio. The thicker the thickness is, the higher the contrastratio can be realized, and thus it is not particularly limited, but itmay be generally about 30 μm or less, 25 μm or less, 20 μm or less, or15 μm or less.

Such an active liquid crystal layer or the liquid crystal element filmcomprising the same may switch between a first oriented state and asecond oriented state different from the first oriented state. Theswitching may be controlled, for example, through application ofexternal energy such as a voltage. For example, any one of the first andsecond oriented states may be maintained in a state where the voltage isnot applied, and then switched to the other oriented state by applying avoltage.

In one example, the first and second oriented states may be eachselected from a horizontal orientation, vertical orientation, twistednematic orientation, or cholesteric orientation state. For example, inthe black mode, the liquid crystal element or the liquid crystal layermay be at least in horizontal orientation, twisted nematic orientationor cholesteric orientation, and in the transparent mode, the liquidcrystal element or liquid crystal layer may be in a vertically orientedstate, or a horizontally oriented state having optical axes ofdirections different from the horizontal orientation of the black mode.The liquid crystal element may be an element of a normally black mode inwhich the black mode is implemented in a state where a voltage is notapplied, or may implement a normally transparent mode in which thetransparent mode is implemented in a state where a voltage is notapplied.

A method of confirming which direction the optical axis of the liquidcrystal layer is formed in the oriented state of the liquid crystallayer is known. For example, the direction of the optical axis of theliquid crystal layer can be measured by using another polarizing platewhose optical axis direction is known, which can be measured using aknown measuring instrument, for example, a polarimeter such as Pascal2000 from Jasco.

A method of realizing the liquid crystal element of the normallytransparent or black mode by adjusting the dielectric constantanisotropy of the liquid crystal host, the alignment direction of thealignment film for orienting the liquid crystal host or the like isknown.

The liquid crystal element film may comprise two base films disposedopposite to each other and the active liquid crystal layer between thetwo base films.

The liquid crystal element film may further comprise spacers formaintaining an interval of the two base films between the two base filmsand/or a sealant for attaching the base films in a state where theinterval of two base films disposed opposite to each other ismaintained. As the spacer and/or the sealant, a known material can beused without any particular limitation.

As the base film, for example, an inorganic film made of glass or thelike, or a plastic film can be used. As the plastic film, a TAC(triacetyl cellulose) film; a COP (cycloolefin copolymer) film such asnorbornene derivatives; an acryl film such as PMMA (poly(methylmethacrylate); a PC (polycarbonate) film; a PE (polyethylene) film; a PP(polypropylene) film; a PVA (polyvinyl alcohol) film; a DAC (diacetylcellulose) film; a Pac (polyacrylate) film; a PES (polyether sulfone)film; a PEEK (polyetheretherketone) film; a PPS (polyphenylsulfone)film, a PEI (polyetherimide) film; a PEN (polyethylenenaphthatate) film;a PET (polyethyleneterephtalate) film; a PI (polyimide) film; a PSF(polysulfone) film; a PAR (polyarylate) film or a fluororesin film andthe like can be used, without being limited thereto. A coating layer ofgold, silver, or a silicon compound such as silicon dioxide or siliconmonoxide, or a coating layer such as an antireflection layer may also bepresent on the base film, if necessary.

As the base film, a film having a phase difference in a predeterminedrange may be used, or an isotropic film may be used. In one example, thebase film may have a front phase difference of 100 nm or less. Inanother example, the front phase difference may be about 95 nm or less,about 90 nm or less, about 85 nm or less, about 80 nm or less, about 75nm or less, about 70 nm or less, about 65 nm or less, about 60 nm orless, about 55 nm or less, about 50 nm or less, about 45 nm or less,about 40 nm or less, about 35 nm or less, about 30 nm or less, about 25nm or less, about 20 nm or less, about 15 nm or less, about 10 nm orless, about 5 nm or less, about 4 nm or less, about 3 nm or less, orabout 2 nm or less, about 1 nm or less, or about 0.5 nm or less. Inanother example, the front phase difference may be about 0 nm or more,about 1 nm or more, about 2 nm or more, about 3 nm or more, about 4 nmor more, about 5 nm or more, about 6 nm or more, about 7 nm or more,about 8 nm or more, about 9 nm or more, or about 9.5 nm or more.

An absolute value of a thickness direction phase difference of the basefilm may be, for example, 200 nm or less. The absolute value of thethickness direction phase difference may be 190 nm or less, 180 nm orless, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less,130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm orless, 85 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nmor less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 5nm or less, 4 nm or less, 3 nm or less, 2 nm or less, 1 nm or less, or0.5 nm or less, and may be 0 nm or more, 10 nm or more, 20 nm or more,30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm ormore, or 75 nm or more. The thickness direction phase difference may benegative, or may be positive, if the absolute value is within the aboverange, and for example, may be negative.

However, as the base film, a high phase difference base film, in whichthe front phase difference is about 2,000 nm or more, 3,000 nm or more,4,000 nm or more, 5,000 nm or more, 6,000 nm or more, 7,000 nm or more,or 7,500 nm or more, and/or the thickness direction phase difference isabout 2000 nm or more, 3,000 nm or more, 4,000 nm or more, 5,000 nm ormore, 6,000 nm or more, 7,000 nm or more, about 8,000 nm or more, about9,000 nm or more, or about 10,000 nm or more, may also be used. Theupper limit of the front phase difference or the thickness directionphase difference of the high phase difference base film is notparticularly limited, and for example, a base film having a front phasedifference of about 10,000 nm or less and/or a thickness direction phasedifference of about 15,000 nm or less may also be applied.

In this specification, the front phase difference (Rin) is a numericalvalue calculated by Equation 1 below, and the thickness direction phasedifference (Rth) is a numerical value calculated by Equation 2 below.Unless otherwise specified, the reference wavelength of the front andthickness direction phase differences is about 550 nm.

Front phase difference (Rin)=d×(nx−ny)  [Equation 1]

Thickness direction phase difference (Rth)=d×(nz−ny)  [Equation 2]

In Equations 1 and 2, d is the thickness of the base film, nx is therefractive index in the slow axis direction of the base film, ny is therefractive index in the fast axis direction of the base film, and nz isthe refractive index in the thickness direction of the base film.

When the base film is optically anisotropic, the angle formed by theslow axes of the base films disposed opposite to each other may be, forexample, in a range of about −10 degrees to 10 degrees, in a range of −7degrees to 7 degrees, in a range of −5 degrees to 5 degrees or in arange of −3 degrees to 3 degrees, or may be approximately parallel.

The angle formed by the slow axis of the base film and a lightabsorption axis of a polarizer to be described below may be, forexample, in a range of about −10 degrees to 10 degrees, in a range of −7degrees to 7 degrees, in a range of −5 degrees to 5 degrees or in arange of −3 degrees to 3 degrees, or may be approximately parallel, ormay be in a range of about 80 degrees to 100 degrees, in a range ofabout 83 degrees to 97 degrees, in a range of about 85 degrees to 95degrees or in a range of about 87 degrees to 92 degrees, or may beapproximately vertical.

It is possible to realize optically excellent and uniform transparentand black modes through the phase difference adjustment or thearrangement of the slow axes.

The base film may have a coefficient of thermal expansion of 100 ppm/Kor less. In another example, the coefficient of thermal expansion may be95 ppm/K or less, 90 ppm/K or less, 85 ppm/K or less, 80 ppm/K or less,75 ppm/K or less, 70 ppm/K or less, or 65 ppm/K or less, or may be 10ppm/K or more, 20 ppm/K or more, 30 ppm/K or more, 40 ppm/K or more, 50ppm/K or more, or 55 ppm/K or more. For example, the coefficient ofthermal expansion of the base film may be measured in accordance withthe provisions of ASTM D696, may be calculated by tailoring the film inthe form provided in the relevant standard and measuring the change inlength per unit temperature, or may be measured by a known method suchas TMA (thermomechanic analysis).

As the base film, a base film having an elongation at break of about 2%or more may be used. In another example, the elongation at break may beabout 4% or more, about 8% or more, about 10% or more, about 12% ormore, about 14% or more, about 16% or more, about 20% or more, about 30%or more, about 40% or more, about 50% or more, about 60% or more, about70% or more, about 80% or more, about 90% or more, 95% or more, 100% ormore, 105% or more, 110% or more, 115% or more, 120% or more, 125% ormore, 130% or more, 135% or more, 140% or more, 145% or more, 150% ormore, 155% or more, 160% or more, 165% or more, 170% or more, or 175% ormore, and may be 1,000% or less, 900% or less, 800% or less, 700% orless, 600% or less, 500% or less, 400% or less, 300% or less, or 200% orless. The elongation at break of the base film may be measured inaccordance with ASTM D882 standard, and may be measured by tailoring thefilm in the form provided by the corresponding standard and usingequipment capable of measuring stress-strain curve (capable ofsimultaneously measuring force and length). Furthermore, the elongationat break may be, for example, a numerical value for any one of the MD(mechanical direction) direction or the TD (transverse direction)direction of the base film.

By selecting the base film to have such a coefficient of thermalexpansion and/or elongation at break, an optical device having excellentdurability can be provided.

The thickness of the base film as above is not particularly limited, andfor example, may be in a range of about 50 μm to 200 μm or so. Thethickness of the base film may be changed as necessary.

Among physical properties mentioned herein, when the measuringtemperature or pressure influences the result, the correspondingphysical property is measured at normal temperature and normal pressure,unless otherwise specified.

The term normal temperature is a natural temperature without warming orcooling, which may be generally any one temperature in a range of about10° C. to 30° C., for example, a temperature of about 23° C. or about25° C. or so. Unless otherwise specified herein, the temperature is aCelsius temperature and the unit is ° C.

The term normal pressure is a natural pressure without lowering orelevating, which generally means a pressure of about one atmosphere,such as atmospheric pressure.

In the liquid crystal element film, a conductive layer and/or analignment film may be present on one side of the base film, for example,on the side facing the active liquid crystal layer.

The conductive layer present on the side of the base film is aconstitution for applying a voltage to the active liquid crystal layer,to which a known conductive layer can be applied without any particularlimitation. As the conductive layer, for example, a conductive polymer,a conductive metal, a conductive nanowire, or a metal oxide such as ITO(indium tin oxide) can be applied. Examples of the conductive layer thatcan be applied in the present application are not limited to the above,and all kinds of conductive layers known to be applicable to the liquidcrystal element film in this field can be used.

In one example, an alignment film exists on the side of the base film.For example, a conductive layer may first be formed on one side of thebase film, and an alignment film may be formed on its upper part.

The alignment film is a constitution for controlling orientation of theliquid crystal host included in the active liquid crystal layer, and aknown alignment film can be applied without particular limitation. Asthe alignment film known in the industry, there is a rubbing alignmentfilm or a photo alignment film, and the like, and the alignment filmthat can be used in the present application is the known alignment film,which is not particularly limited.

The alignment direction of the alignment film can be controlled toachieve the orientation of the above-described optical axis. Forexample, the alignment directions of two alignment films formed on eachside of two base films disposed opposite to each other may form an anglein a range of about −10 degrees to 10 degrees, an angle in a range of −7degrees to 7 degrees, an angle in a range of −5 degrees to 5 degrees oran angle in a range of −3 degrees to 3 degrees to each other, or may beapproximately parallel to each other. In another example, the alignmentdirections of the two alignment films may form an angle in a range ofabout 80 degrees to 100 degrees, an angle in a range of about 83 degreesto 97 degrees, an angle in a range of about 85 degrees to 95 degrees oran angle in a range of about 87 degrees to 92 degrees, or may beapproximately perpendicular to each other. In another example, thealignment directions of the two alignment films may form an angle in arange of about 160 degrees to 200 degrees, an angle in a range of about170 degrees to 190 degrees, an angle in a range of about 175 degrees to185 degrees or an angle of about 180 degrees.

Since the direction of the optical axis of the active liquid crystallayer is determined in accordance with such an alignment direction, thealignment direction can be confirmed by checking the direction of theoptical axis of the active liquid crystal layer.

The shape of the liquid crystal element film having such a structure isnot particularly limited, which may be determined according to theapplication of the optical device, and is generally in the form of afilm or a sheet.

In one example, the liquid crystal element film may be in the form of afolded film. The cross-sectional shape of the liquid crystal elementfilm with the folded film type may include a first portion and a secondportion separated by the folded portion of the film. In one example, thecurvature (=1/curvature radius) of the first line in the cross-sectionof the active liquid crystal element film may be in a range of 0 to 0.01at the time of observing the cross-section, and the cross-section mayhave a folded portion at the end of the first portion and include asecond portion connected to the folded portion. That is, the activeliquid crystal element film may be contained in the optical device in afolded state at the folded portion. In another example, the curvature ofthe first line may be about 0.009 or less, 0.008 or less, 0.007 or less,0.006 or less, 0.005 or less, 0.004 or less, 0.003 or less, 0.002 orless, 0.001 or less, 0.0009 or less, 0.0008 or less, 0.0007 or less,0.0006 or less, 0.0005 or less, 0.0004 or less, 0.0003 or less, 0.0002or less, 0.0001 or less, 0.00009 or less, 0.00008 or less, 0.00007 orless, 0.00006 or less, or 0.00005 or less.

In this specification, the curvature or curvature radius may be measuredin a manner known in the industry, and for example, may be measuredusing a contactless apparatus such as a 2D profile laser sensor, achromatic confocal line sensor or a 3D measuring conforcal microscopy.The method of measuring the curvature or curvature radius using such anapparatus is known.

With respect to the curvatures or curvature radius, for example, whenthe curvatures or curvature radii are different on the surface and theback surface of the object to which the curvature or curvature radius isreferred (for example, when the curvatures or curvature radii in thesurface and the back surface of the liquid crystal element filmcorresponding to the first line are different), a small value, a largevalue or an arithmetic average value of curvatures or curvature radii ofthe surface and the back surface may be designated as the curvature orcurvature radius. Furthermore, when the curvatures or curvature radiiare not constant and have different portions, the largest curvature orcurvature radius, or the smallest curvature or curvature radius or theaverage value of curvatures or curvature radii may be a reference.

Furthermore, in this specification, the unit of curvature radius is R,and the unit of curvature is 1/R. Here, R denotes a curved gradient of acircle having a radius of 1 mm. Thus, here, for example, 100R is thedegree of curvature of a circle with a radius of 100 mm or the curvatureradius for such a circle. In the case of a flat surface, the curvatureis zero and the curvature radius is infinite.

As described below, in the optical device of the present application,the active liquid crystal element film and/or the polarizer may beencapsulated in a state where the active liquid crystal element filmand/or the polarizer are positioned inside two outer substrates toconstitute an optical device. Such an encapsulated structure greatlyimproves durability and weatherability of the optical device, and as aresult, it can be stably applied to outdoor applications such assunroofs. However, such an encapsulation process generally requires avacuum compression process such as an autoclave, and in the process,there is a problem that defects such as wrinkles occur in the activeliquid crystal element film, and the like. In addition, when the opticaldevice is exposed to high temperature and/or high humidity conditions,and the like, or in the process, defects such as wrinkles are formed onthe liquid crystal element film by the difference in coefficient ofthermal expansion between the base film of the liquid crystal elementfilm and an adhesive film (encapsulating agent) attached thereto, andthe like, such defects adversely affect the performance of the opticaldevice.

Thus, in the present application, it has been confirmed that the aboveproblem can be solved when the active liquid crystal element film isimplemented with the folded structure.

FIG. 1 is a diagram schematically showing a cross-section of the activeliquid crystal element film (10) having the folded film shape.

As in FIG. 1, the cross-section of the active liquid crystal elementfilm (10) may have a cross-section in the form in which a first portion(101), a folded portion (A) and a second portion (102) are connected.

Here, the first portion (101) may be an active area, that is, an areaserving to modulate light in order to substantially control a lighttransmission state. Such a first portion (101) may be a planar shape,which has a curvature of approximately 0, or may also be a curved shape,such as a convex shape or a concave shape.

As shown in FIG. 1, the liquid crystal element film (10) has a foldedstructure based on the folded portion (A), and thus a second portion(102) is formed. At this time, the degree to which the second portion(102) is folded is not particularly limited as long as it is controlledto such an extent that defects such as wrinkles of the liquid crystalelement film (10) do not occur in the optical device. In one example,the degree of folding may be set such that the angle formed by the firstportion (101) or the tangent (T) of the first portion (101) and thesecond portion (102) is, in a clockwise or counterclockwise direction,more than 0 degrees, 5 degrees or more, 10 degrees or more, 15 degreesor more, 20 degrees or more, 25 degrees or more, 30 degrees or more, 35degrees or more, 40 degrees or more, 45 degrees or more, 50 degrees ormore, 55 degrees or more, 60 degrees or more, 65 degrees or more, 70degrees or more, 75 degrees or more, 80 degrees or more, or 85 degreesor more or so. In another example, the angle may be 180 degrees or less,170 degrees or less, 160 degrees or less, 150 degrees or less, 140degrees or less, 130 degrees or less, 120 degrees or less, 110 degreesor less, 100 degrees or less, or 95 degrees or less or so. Here, thetangent at which the angle with the second portion (102) is measured isa tangent at the point (D) which divides the first portion (101)approximately by two. Also, the second line for measuring the angle forthe tangent (T) may be a line (1022) connecting the folded portion (A)to the point where the second portion (102) is terminated, as shown inFIG. 1. Furthermore, as described below, when the second portion (102)is also in a folded form, the second line for measuring the angle forthe tangent (T) may be a line connecting a folded portion (A in FIG. 1)separating the first portion and the second portion, and a foldedportion in the second line, or may be, the same as above, a lineconnecting the point where the second portion is terminated.

Furthermore, in this specification, the angle formed by the portion lineor the tangent of the first portion and the second portion may be simplyreferred to as a folded angle of an active liquid crystal element film.

The ratio (L1/L2) of the length (L1) of the first portion (101) to thelength (L2) of the second portion (102) may be in a range of about 1.5to 20,000. In another example, the ratio (L1/L2) may be about 2 or more,about 4 or more, about 6 or more, about 8 or more, about 10 or more,about 12 or more, about 14 or more, about 16 or more, about 18 or more,about 20 or more, about 25 or more, about 30 or more, about 35 or more,about 40 or more, about 45 or more, about 50 or more, about 55 or more,about 60 or more, about 65 or more, about 70 or more, about 75 or more,about 80 or more, about 85 or more, about 90 or more, about 95 or more,about 100 or more, about 110 or more, about 120 or more, about 130 ormore, about 140 or more, about 150 or more, about 160 or more, about 170or more, about 180 or more, about 190 or more, about 200 or more, about250 or more, about 300 or more, about 350 or more, about 400 or more,about 450 or more, about 500 or more, about 550 or more, about 600 ormore, about 650 or more, about 700 or more, about 800 or more, about 900or more, about 1000 or more, about 1100 or more, about 1200 or more,about 1500 or more, 2000 or more, 2500 or more, 3000 or more, or 3500 ormore, and may be 3500 or less, 3000 or less, 2900 or less, 2800 or less,2700 or less, 2600 or less, 2500 or less, 2400 or less, 2300 or less,2200 or less, 2100 or less, 2000 or less, about 1,900 or less, about1,800 or less, about 1,700 or less, about 1,600 or less, about 1,500 orless, about 1,400 or less, about 1,300 or less, about 1,200 or less,about 1,100 or less, about 1,000 or less, about 900 or less, about 800or less, about 750 or less, about 700 or less, about 650 or less, about600 or less, about 550 or less, about 500 or less, about 450 or less,about 400 or less, about 350 or less, about 300 or less, about 250 orless, about 200 or less, about 150 or less, about 100 or less, about 50or less, about 45 or less, about 40 or less, about 35 or less, about 30or less, about 25 or less, about 20 or less, or about 15 or less.

In such a relationship, the absolute lengths of the first portion (101)and the second portion (102) are not particularly limited, which may bedetermined according to the intended use of the optical device or thelike. For example, the length of the first portion (101) may be adjustedto be about 100 to 1,000 mm or so. In another example, the length of thefirst portion (101) may be about 150 mm or more, about 200 mm or more,or about 250 mm or more. In another example, the length of the firstportion (101) may be about 900 mm or less, about 800 mm or less, about700 mm or less, about 600 mm or less, about 500 mm or less, about 400 mmor less, about 350 mm or less, or about 300 mm or less.

In addition, as described below, when a plurality of second portions areformed in the cross-section of the active liquid crystal element film,the length of the second portion introduced into the ratio (L1/L2)calculation may be a length of any one portion of the plurality ofsecond portions, or may be the sum of the lengths of the secondportions.

The folded structure may be formed at both ends in the cross-section ofthe liquid crystal element film. Accordingly, as in FIG. 1, the foldedportions (A) and the second portions (102) may be formed at both ends ofthe first portion (101) in the cross-section of the active liquidcrystal element film.

In such a structure, the second line may be further folded, and forexample, as shown in FIG. 2, a second folded portion (AA) exists on thesecond portion (102), where the cross-section in the form that thesecond portion (102) is further folded in the folded portion (AA) may berealized.

In this case, the forming position of the additionally formed foldedportion (AA) is not particularly limited, and for example, the positionmay be adjusted so that the distance from the folded area (A) formed atthe connecting portion of the first portion (101) and the second portion(102) to the folded area (AA) formed on the second portion (102) becomesL2 satisfying the above-mentioned ratio (L1/L2).

The cross-section of the liquid crystal element film in which such across-section is observed is a cross-section observed when the liquidcrystal element film has been observed from any side. That is, thecross-section is preferably observed on any one side of the sides of theliquid crystal element film.

In one example, the cross-section in which the folded structure isobserved may be a cross-section on a normal plane formed by includingthe long axis or the short axis of the liquid crystal element film.Here, for example, in the case where the liquid crystal element film(10) is observed from above, when it is the rectangular shape as in FIG.3, the long axis may be the long side (LA) of horizontal and verticallengths, and the short axis may be the short side (SA).

For example, the cross-sectional structure may be realized by folding aportion indicated by a dotted line in the liquid crystal element film(10) having the same structure as FIG. 3.

When the liquid crystal element film has a square shape, any one of thehorizontal axis and the vertical axis may be regarded as the long axisand the other may be regarded as the short axis.

Furthermore, in the case of a shape other than a rectangular shape, forexample, in the case of an elliptical, circular or amorphous shape, andthe like, when the liquid crystal element film is observed from above, aline perpendicular to the line formed by the folded portion (forexample, a dotted line in FIG. 3) may be any one of the short axis andthe long axis, and a line which is again perpendicular to the line maybe the other of the short axis and the long axis.

In one example, as shown in FIG. 3, all four sides of the liquid crystalelement film can be folded to form the cross-section, and in this case,the cross-section may be observed on both the normal plane including thelong axis of the liquid crystal element film and the normal planeincluding the short axis.

Although the position of the above-mentioned sealant in the liquidcrystal element film having such a folded structure is not particularlylimited, generally, the sealant attaching the two base films may existin the folded portion (A in FIGS. 1 and 2) or an area facing from thefolded portion (A in FIGS. 1 and 2) toward the first portion (101).

The optical device may further comprise a polarizer together with theactive liquid crystal element film. As the polarizer, for example, anabsorbing or reflecting linear polarizer, that is, a polarizer having alight absorption axis or a light reflection layer formed in onedirection and a light transmission axis formed approximatelyperpendicular thereto may be used.

Assuming that the blocking state is implemented in the first orientedstate of the active liquid crystal layer, the polarizer may be disposedin the optical device such that the angle formed by an average opticalaxis (vector sum of optical axes) of the first oriented state and thelight absorption axis of the polarizer is 80 degrees to100 degrees or 85degrees to 95 degrees, or it is approximately perpendicular, or may bedisposed in the optical device such that it is 35 degrees to 55 degreesor 40 degrees to 50 degrees or about 45 degrees.

When the alignment direction of the alignment film is used as areference, the alignment directions of the alignment films formed oneach side of the two base films of the liquid crystal element filmdisposed opposite to each other as described above may form, to eachother, an angle in a range of about −10 degrees to 10 degrees, an anglein a range of −7 degrees to 7 degrees, an angle in a range of −5 degreesto 5 degrees or an angle in a range of −3 degrees to 3 degrees, or inthe case of being approximately parallel to each other, the angle formedby the alignment direction of any one of the two alignment films and thelight absorption axis of the polarizer may be 80 degrees to 100 degreesor 85 to 95 degrees, or may be approximately perpendicular.

In another example, the alignment directions of the two alignment filmsmay form an angle in a range of about 80 degrees to 100 degrees, anangle in a range of about 83 degrees to 97 degrees, an angle in a rangeof about 85 degrees to 95 degrees or an angle in a range of about 87degrees to 92 degrees, or in the case of being approximately vertical toeach other, the angle formed by the alignment direction of the alignmentfilm disposed closer to the polarizer of the two alignment films and thelight absorption axis of the polarizer may be 80 degrees to 100 degreesor 85 degrees to 95 degrees, or may be approximately perpendicular.

For example, as shown in FIG. 4, the liquid crystal element film (10)and the polarizer (20) may be disposed in a state of being laminated oneach other such that the optical axis (average optical axis) of thefirst alignment direction in the liquid crystal element film (10) andthe light absorption axis of the polarizer (20) become the aboverelationship.

In one example, when the polarizer (20) is a polarizing coating layer tobe described below, a structure in which the polarizing coating layer ispresent inside the liquid crystal element film can be realized. Forexample, as shown in FIG. 5, a structure in which the polarizing coatinglayer (201) is present between any one base film (110) of the base films(110) of the liquid crystal element film and the active liquid crystallayer (120) can be realized. For example, the conductive layer, thepolarizing coating layer (201) and the alignment film as described abovemay be sequentially formed on the base film (110).

The kind of the polarizer that can be applied in the optical device ofthe present application is not particularly limited. For example, as thepolarizer, a conventional material used in conventional LCDs or thelike, such as a PVA (poly(vinyl alcohol)) polarizer, or a polarizerimplemented by a coating method such as a polarizing coating layercomprising lyotropic liquid crystals (LLCs) or reactive mesogens (RMs)and a dichroic dye can be used. In this specification, the polarizerimplemented by the coating method as described above may be referred toas a polarizing coating layer. As the lyotropic liquid crystal, a knownliquid crystal may be used without any particular limitation, and forexample, a lyotropic liquid crystal capable of forming a lyotropicliquid crystal layer having a dichroic ratio of about 30 to 40 or so maybe used. On the other hand, when the polarizing coating layer containsreactive mesogens (RMs) and a dichroic dye, as the dichroic dye, alinear dye may be used, or a discotic dye may also be used.

Mixtures of lyotropic liquid crystals or reactive mesogens and adichroic dye that can act as an absorbing or reflecting linear polarizerare variously known in the industry, and such a kind can be appliedwithout limitation to the present application.

The optical device of the present application may comprise only each oneof the active liquid crystal element film and the polarizer as describedabove. Thus, the optical device may comprise only one active liquidcrystal element film and may comprise only one polarizer.

The optical device may further comprise two outer substrates disposedopposite to each other. For example, as shown in FIG. 6, the activeliquid crystal element film (10) and the polarizer (20) may existbetween the two substrates (30) disposed opposite to each other. FIG. 6has illustrated the case where the active liquid crystal element film(10) and the polarizer (20) are present simultaneously between the outersubstrate (30) and the polarizer (20), but the structure is exemplary,where only any one of the film (10) or the polarizer (20) may alsoexist. Also, the polarizer (20) in FIG. 6 does not exist, and only theactive liquid crystal element film including the polarizing coatinglayer (201) as shown in FIG. 5 may also exist between the outersubstrates (30).

As the outer substrate, for example, an inorganic film made of glass orthe like, or a plastic film can be used. As the plastic film, a TAC(triacetyl cellulose) film; a COP (cycloolefin copolymer) film such asnorbornene derivatives; an acryl film such as PMMA (poly(methylmethacrylate); a PC (polycarbonate) film; a PE (polyethylene) film; a PP(polypropylene) film; a PVA (polyvinyl alcohol) film; a DAC (diacetylcellulose) film; a Pac (polyacrylate) film; a PES (polyether sulfone)film; a PEEK (polyetheretherketone) film; a PPS (polyphenylsulfone)film, a PEI (polyetherimide) film; a PEN (polyethylenenaphthatate) film;a PET (polyethyleneterephtalate) film; a PI (polyimide) film; a PSF(polysulfone) film; a PAR (polyarylate) film or a fluororesin film andthe like can be used, without being limited thereto. A coating layer ofgold, silver, or a silicon compound such as silicon dioxide or siliconmonoxide, or a coating layer such as an antireflection layer may also bepresent on the outer substrate, if necessary.

As the outer substrate, a film having a phase difference in apredetermined range may be used. In one example, the outer substrate mayhave a front phase difference of 100 nm or less. In another example, thefront phase difference may be about 95 nm or less, about 90 nm or less,about 85 nm or less, about 80 nm or less, about 75 nm or less, about 70nm or less, about 65 nm or less, about 60 nm or less, about 55 nm orless, about 50 nm or less, about 45 nm or less, about 40 nm or less,about 35 nm or less, about 30 nm or less, about 25 nm or less, about 20nm or less, about 15 nm or less, about 10 nm or less, about 9 nm orless, about 8 nm or less, about 7 nm or less, about 6 nm or less, about5 nm or less, about 4 nm or less, about 3 nm or less, or about 2 nm orless, or about 1 nm or less. In another example, the front phasedifference may be about 0 nm or more, about 1 nm or more, about 2 nm ormore, about 3 nm or more, about 4 nm or more, about 5 nm or more, about6 nm or more, about 7 nm or more, about 8 nm or more, about 9 nm ormore, or about 9.5 nm or more.

An absolute value of a thickness direction phase difference of the outersubstrate may be, for example, 200 nm or less. The absolute value of thethickness direction phase difference may be 190 nm or less, 180 nm orless, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less,130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm orless, 85 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nmor less, 40 nm or less, 30 nm or less, 20 nm or less, about 15 nm orless, about 10 nm or less, about 9 nm or less, about 8 nm or less, about7 nm or less, about 6 nm or less, about 5 nm or less, about 4 nm orless, about 3 nm or less, about 2 nm or less, or about 1 nm or less, andmay be 0 nm or more, 5 nm or more, 10 nm or more, 20 nm or more, 30 nmor more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or75 nm or more. The thickness direction phase difference may be negative,or may be positive, if the absolute value is within the above range, andfor example, may be negative.

The front phase difference (Rin) and the thickness direction phasedifference (Rth) of the outer substrate may be calculated in the samemanner, except that in Equations 1 and 2 above, the thickness (d), therefractive index in the slow axis direction (nx), the refractive indexin the fast axis direction (ny) and the refractive index in thethickness direction (nz) are substituted with the thickness (d), therefractive index in the slow axis direction (nx), the refractive indexin the fast axis direction (ny) and the refractive index in thethickness direction (nz), of the outer substrate, respectively, tocalculate them.

When the outer substrate is optically anisotropic, the angle formed bythe slow axes of the outer substrates disposed opposite to each othermay be, for example, in a range of about −10 degrees to 10 degrees, in arange of −7 degrees to 7 degrees, in a range of −5 degrees to 5 degreesor in a range of −3 degrees to 3 degrees, or may be approximatelyparallel.

Also, the angle formed by the slow axis of the outer substrate and, inthe case where the above-described base film is optically anisotropic,the slow axis of the base film may be, for example, in a range of about−10 degrees to 10 degrees, in a range of −7 degrees to 7 degrees, in arange of −5 degrees to 5 degrees or in a range of −3 degrees to 3degrees, or may be approximately parallel, or may be in a range of about80 degrees to 100 degrees, in a range of about 83 degrees to 97 degrees,in a range of about 85 degrees to 95 degrees or in a range of about 87degrees to 92 degrees, or may be approximately vertical.

It is possible to realize optically excellent and uniform transparentand black modes through the phase difference adjustment or thearrangement of the slow axes.

As the outer substrate, a substrate having a coefficient of thermalexpansion of 100 ppm/K or less may be used. In another example, thecoefficient of thermal expansion may be 95 ppm/K or less, 90 ppm/K orless, 85 ppm/K or less, 80 ppm/K or less, 75 ppm/K or less, 70 ppm/K orless, 65 ppm/K or less, 60 ppm/K or less, 50 ppm/K or less, 40 ppm/K orless, 30 ppm/K or less, 20 ppm/K or less, or 15 ppm/K or less, or may be1 ppm/K or more, 2 ppm/K or more, 3 ppm/K or more, 4 ppm/K or more, 5ppm/K or more, 6 ppm/K or more, 7 ppm/K or more, 8 ppm/K or more, 9ppm/K or more, or 10 ppm/K or more.

The methods of measuring the coefficient of thermal expansion and theelongation at break of the outer substrate are the same as the methodsof measuring the coefficient of thermal expansion and elongation atbreak of the base film as described above.

By selecting the outer substrate to have such a coefficient of thermalexpansion and/or elongation at break, an optical device having excellentdurability can be provided.

The thickness of the outer substrate as above is not particularlylimited, and for example, may be about 0.3 mm or more. In anotherexample, the thickness may be about 0.5 mm or more, about 1 mm or more,about 1.5 mm or more, or about 2 mm or more or so, and may also be 10 mmor less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm orless, 4 mm or less, or 3 mm or less or so.

The outer substrate may be a flat substrate or may be a substrate havinga curved surface shape. For example, the two outer substrates may besimultaneously flat substrates, simultaneously have a curved surfaceshape, or any one may be a flat substrate and the other may be asubstrate having a curved surface shape.

In addition, in the case of having the curved surface shape at the sametime, the respective curvatures or curvature radii may be the same ordifferent.

The curvature or curvature radius of the outer substrate can be measuredin the above-described manner.

Also, regarding the outer substrate, for example, when the curvatures orthe curvature radii at the front surface and the back surface aredifferent from each other, the curvatures or curvature radii of therespective facing surfaces, that is, the curvature or curvature radiusof the surface facing a second outer substrate in the case of a firstouter substrate and the curvature or curvature radius of the surfacefacing the first outer substrate in the case of the second outersubstrate may be a reference. Furthermore, when the relevant surface hasportions that the curvatures or curvature radii are not constant anddifferent, the largest curvature or curvature radius, or the smallestcurvature or curvature radius, or the average curvature or averagecurvature radius may be a reference.

Both of the substrates may have a difference in curvature or curvatureradius within 10%, within 9%, within 8%, within 7%, within 6%, within5%, within 4%, within 3%, within 2% or within 1%. When a large curvatureor curvature radius is C_(L) and a small curvature or curvature radiusis C_(S), the difference in curvature or curvature radius is a valuecalculated by 100×(C_(L)−C_(S))/C_(S). In addition, the lower limit ofthe difference in curvature or curvature radius is not particularlylimited. Since the differences in curvatures or curvature radii of twoouter substrates can be the same, the difference in curvature orcurvature radius may be 0% or more, or more than 0%.

The control of such a curvature or curvature radius is useful in astructure in which an active liquid crystal element and/or a polarizerare encapsulated by an adhesive film as in the optical device of thepresent application.

When both the first and second outer substrates are curved surfaces,both curvatures may have the same sign. In other words, the two outersubstrates may be bent in the same direction. That is, in the abovecase, both the center of curvature of the first outer substrate and thecenter of curvature of the second outer substrate exist in the sameportion of the upper part and the lower part of the first and secondouter substrates.

The specific range of each curvature or curvature radius of the firstand second outer substrates is not particularly limited. In one example,the curvature radius of each substrate may be 100R or more, 200R ormore, 300R or more, 400R or more, 500R or more, 600R or more, 700R ormore, 800R or more, or 900R or more, or may be 10,000R or less, 9,000Ror less, 8,000R or less, 7,000R or less, 6,000R or less, 5,000R or less,4,000R or less, 3,000R or less, 2,000R or less, 1,900R or less, 1,800Ror less, 1,700R or less, 1,600R or less, 1,500R or less, 1,400R or less,1,300R or less, 1,200R or less, 1,100R or less, or 1,050R or less. Here,R denotes a curved gradient of a circle having a radius of 1 mm. Thus,here, for example, 100R is the degree of curvature of a circle with aradius of 100 mm or the curvature radius for such a circle. Of course,in the case of a flat surface, the curvature is zero and the curvatureradius is infinite.

The first and second outer substrates may have the same or differentcurvature radii in the above range. In one example, when the curvaturesof the first and second outer substrates are different from each other,the curvature radius of the substrate having a large curvature amongthem may be within the above range.

In one example, when the curvatures of the first and second outersubstrates are different from each other, a substrate having a largecurvature among them may be a substrate that is disposed in the gravitydirection upon using the optical device.

That is, for the encapsulation, an autoclave process using an adhesivefilm may be performed, as described below, and in this process, hightemperature and high pressure are usually applied. However, in somecases, such as when the adhesive film applied to the encapsulation isstored at a high temperature for a long time after such an autoclaveprocess, some re-melting or the like occurs, so that there may be aproblem that the outer substrates are widening. If such a phenomenonoccurs, a force may act on the encapsulated active liquid crystalelement and/or polarizer, and bubbles may be formed inside.

However, when the curvatures or curvature radii between the substratesare controlled as described above, even if the adhesion force by theadhesive film is lowered, a net force which is the sum of the restoringforce and the gravity may act thereon to prevent the widening and alsoto withstand the same process pressure as the autoclave.

The optical device may further comprise an adhesive film encapsulatingthe active liquid crystal element film and/or the polarizer in the outersubstrates. For example, as shown in FIG. 7, the adhesive film (40) maybe present between the outer substrate (30) and the active liquidcrystal element film (10), between the active liquid crystal elementfilm (10) and the polarizer (20) and/or between the polarizer (20) andthe outer substrate (30). In addition, the adhesive film (40) may bepresent on the sides of the active liquid crystal element film (10)and/or the polarizer (20), appropriately, on all sides, as shown in thedrawing. The adhesive film may encapsulate the active liquid crystalfilm element (10) and the polarizer (20) while attaching the outersubstrate (30) and the active liquid crystal film element (10), theactive liquid crystal film element (10) and the polarizer (20), and thepolarizer (20) and the outer substrate (30) to each other.

Furthermore, as shown in FIG. 5, when the active liquid crystal elementfilm in which the polarizing coating layer (201) is formed inside isencapsulated, the adhesive film may be present between the outersubstrate and the active liquid crystal element film and/or on the sidesof the active liquid crystal element film, preferably, on all sides.

For example, after laminating outer substrates, an active liquid crystalelement film, a polarizer and/or an adhesive film according to a desiredstructure, the above structure can be realized by a method of pressingthem in a vacuum state, for example, an autoclave method.

For efficiently forming such a structure, a friction coefficient of thesurface of the active liquid crystal element film contacting theadhesive film against the adhesive film or a friction coefficientbetween the active liquid crystal element film and the adhesive film canbe controlled, if necessary. For example, the friction coefficient maybe controlled to about 5 or less, about 4.5 or less, about 4 or less,about 3.5 or less, about 3 or less, or about 2.5 or less or so, and inanother example, the friction coefficient may be about 0.5 or more,about 1 or more, or about 1.5 or more. Through the control of such afriction coefficient, the efficient encapsulation process can proceedwithout generating defects, such as wrinkles, in the liquid crystalelement film in a pressurizing process such as an autoclave. Here, thefriction coefficient is a dynamic friction coefficient.

The method of controlling the friction coefficient is not particularlylimited, and for example, an adhesive film and a base film of an activeliquid crystal element film, which have desired friction coefficients,may be selected, or an appropriate surface treatment may be performed onthe base film. At this time, the surface treatment may controlconcave-convex shapes of the base film, as a physical treatment, forexample, through polishing using a sandpaper or the like, or may controlthe friction coefficient by treating the surface of the base film usinga treating agent known as a so-called release agent or slipping agent,and the like, such as a fluorine-based treating agent or a silicon-basedtreating agent.

As the adhesive film, a known material can be used without anyparticular limitation, and for example, among a known thermoplasticpolyurethane adhesive film, polyamide adhesive film, polyester adhesivefilm, EVA (ethylene vinyl acetate) adhesive film, polyolefin adhesivefilm such as polyethylene or polypropylene, and the like, one satisfyingphysical properties to be described below can be selected.

As the adhesive film, a film having a phase difference in apredetermined range may be used. In one example, the adhesive film mayhave a front phase difference of 100 nm or less. In another example, thefront phase difference may be about 95 nm or less, about 90 nm or less,about 85 nm or less, about 80 nm or less, about 75 nm or less, about 70nm or less, about 65 nm or less, about 60 nm or less, about 55 nm orless, about 50 nm or less, about 45 nm or less, about 40 nm or less,about 35 nm or less, about 30 nm or less, about 25 nm or less, about 20nm or less, about 15 nm or less, about 10 nm or less, about 9 nm orless, about 8 nm or less, about 7 nm or less, about 6 nm or less, about5 nm or less, about 4 nm or less, about 3 nm or less, about 2 nm orless, or about 1 nm or less. The front phase difference may be about 0nm or more, about 1 nm or more, about 2 nm or more, about 3 nm or more,about 4 nm or more, about 5 nm or more, about 6 nm or more, about 7 nmor more, about 8 nm or more, about 9 nm or more, or about 9.5 nm ormore.

An absolute value of the thickness direction phase difference of theadhesive film may be, for example, 200 nm or less. In another example,the absolute value may be about 190 nm or less, 180 nm or less, 170 nmor less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less,120 nm or less, 115 nm or less, 100 nm or less, 90 nm or less, 80 nm orless, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nmor less, 20 nm or less, 10 nm or less, or about 5 nm or less, or may be0 nm or more, 1 nm or more, 2 nm or more, 3 nm or more, 4 nm or more, 5nm or more, 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more, 10nm or more, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more,60 nm or more, 70 nm or more, 80 nm or more, or 90 nm or more. As longas the thickness direction phase difference has an absolute value in theabove range, it may be negative, or may be positive.

The front phase difference (Rin) and the thickness direction phasedifference (Rth) of the adhesive film may be calculated in the samemanner, except that in Equations 1 and 2 above, the thickness (d), therefractive index in the slow axis direction (nx), the refractive indexin the fast axis direction (ny) and the refractive index in thethickness direction (nz) are substituted with the thickness (d), therefractive index in the slow axis direction (nx), the refractive indexin the fast axis direction (ny) and the refractive index in thethickness direction (nz), of the adhesive film, respectively, tocalculate them.

Here, the thickness of the adhesive film may be a thickness of theadhesive film between the outer substrate (30) and the active liquidcrystal layer (10), such as an interval between the two, a thickness ofthe adhesive film between the active liquid crystal layer (10) and thepolarizer (20), such as an interval between the two, and a thickness ofthe adhesive film between the polarizer (20) and the outer substrate(30), such as an interval between the two.

As the adhesive film, one having a Young's modulus in a range of 0.1 to100 MPa may be used. The Young's modulus may be measured in accordancewith ASTM D882 standard, and may be measured by tailoring the film inthe form provided by the corresponding standard and using equipmentcapable of measuring stress-strain curve (capable of simultaneouslymeasuring force and length).

By selecting the adhesive film to have such a Young's modulus, anoptical device with excellent durability can be provided.

The thickness of such an adhesive film is not particularly limited,which may be, for example, in a range of about 200 μm to 600 μm. Here,the thickness of the adhesive film may be a thickness of the adhesivefilm between the outer substrate (30) and the active liquid crystallayer (10), such as an interval between the two, a thickness of theadhesive film between the active liquid crystal layer (10) and thepolarizer (20), such as an interval between the two, and a thickness ofthe adhesive film between the polarizer (20) and the outer substrate(30), such as an interval between the two.

The optical device may further comprise a buffer layer. Such a bufferlayer may be present on one side or both sides of the liquid crystalelement film. FIG. 8 shows a structure in which the buffer layer (50) ispresent on both sides of the active liquid crystal element film (10),but the buffer layer (50) may also be present only on one side of theliquid crystal element film (10).

Such a buffer layer can mitigate the negative pressure caused by thedifference in the coefficient of thermal expansion between layers in astructure in which the active liquid crystal element film isencapsulated by an adhesive film, and enable so that a more durabledevice can be realized.

In one example, as the buffer layer, a layer having a Young's modulus of1 MPa or less may be used. In another example, the Young's modulus ofthe buffer layer may be 0.9 MPa or less, 0.8 MPa or less, 0.7 MPa orless, 0.6 MPa or less, 0.6 MPa or less, 0.1 MPa or less, 0.09 MPa orless, 0.08 MPa or less, 0.07 MPa or less, or 0.06 MPa or less. Inanother example, the Young's modulus is about 0.001 MPa or more, 0.002MPa or more, 0.003 MPa or more, 0.004 MPa or more, 0.005 MPa or more,0.006 MPa or more, 0.007 MPa or more, 0.008 MPa or more, 0.009 MPa ormore, 0.01 MPa or more, 0.02 MPa or more, 0.03 MPa or more, 0.04 MPa ormore, or 0.045 MPa or more. Here, the measurement method of the Young'smodulus is the same as the above-mentioned measuring method of theadhesive film.

As a specific kind of the buffer layer, a transparent material showingthe above-mentioned Young's modulus may be used without particularlimitation, and for example, an acrylate-based, urethane-based,rubber-based or silicone-based oligomer or polymer material, and thelike can be used.

In one example, the buffer layer may be formed using a transparentadhesive or a transparent pressure-sensitive adhesive known as aso-called OCA (optical clear adhesive) or OCR (optical clear resin), anda material having a desired Young's modulus may be selected from theadhesives or the pressure-sensitive adhesives known as the OCA or OCRand used.

Therefore, in one example, the buffer layer may be an acrylate-basedadhesive layer, a urethane-based adhesive layer, a rubber-based adhesivelayer or a silicone-based adhesive layer, or may be an acrylate-basedpressure-sensitive adhesive layer, a urethane-based pressure-sensitiveadhesive layer, a rubber-based pressure-sensitive adhesive layer or asilicone-based pressure-sensitive adhesive layer.

The thickness of the buffer layer is not particularly limited, which maybe selected within a range that can effectively reduce the negativepressure generated inside the device by exhibiting the Young's modulusin the above range.

The optical device may further comprise any necessary configurationother than the above configurations, and for example, comprise a knownconfiguration such as a retardation layer, an optical compensationlayer, an antireflection layer and a hard coating layer in a properposition.

Such an optical element can be used for various applications, and forexample, can be used for eyewear such as sunglasses or AR (augmentedreality) or VR (virtual reality) eyewear, an outer wall of a building ora sunroof for a vehicle, and the like.

In one example, the optical device itself may be a sunroof for avehicle.

For example, in an automobile including a body in which at least oneopening is formed, the optical device or the sunroof for a vehicleattached to the opening can be mounted and used.

Advantageous Effects

The present application provides an optical device capable of varyingtransmittance, and such an optical device can be used for variousapplications such as eyewear, for example, sunglasses or AR (augmentedreality) or VR (virtual reality) eyewear, an outer wall of a building ora sunroof for a vehicle.

MODE FOR INVENTION

Hereinafter, the scope of the present application will be described inmore detail through Examples and Comparative Examples, but the scope ofthe present application is not limited by the following examples.

The physical properties described in this specification are the resultsof evaluation in the following manner.

1. Evaluation of Tensile Properties

Tensile properties of a base film such as elongation at break wereconfirmed according to ASTM D882 standard. Each physical property wasevaluated by tailoring a measuring object such as the base film to havea width of 10 mm and a length of 30 mm and then stretching it at atensile rate of 10 mm/min at room temperature (25° C.) using a UTM(universal testing machine) instrument (Instron 3342).

2. Evaluation of Coefficient of Thermal Expansion

The coefficient of thermal expansion (CTE) of the base film or the likewas measured using a TMA (thermomechanical analysis) instrument(SDTA840, Metteler toledo) according to ASTM D696 standard, wheredimensional changes of a specimen were measured while increasing atemperature from 40° C. to 80° C. at a rate of 10° C./min to confirm thecoefficient of thermal expansion in the section according to an equation(CTE=(dt/t)/dT, where t is a dimension and T is a temperature). Thereference length of the specimen at the time of measurement was set as10 mm, and the load was set as 0.02 N.

3. Evaluation of Friction Coefficient

The measurement of the friction coefficient was performed according tothe standard using the FP-2260 instrument from Thwing Albert InstrumentCompany. Specifically, an adhesive film and an active liquid crystalelement film were overlapped and placed, and a friction force wascalculated through a ratio of the force measured while pulling theinstrument relative to a normal force to obtain a dynamic frictioncoefficient. The sizes of the specimens were each about 4 cm in lengthand about 2 cm in width.

Example 1

A GH (guest-host) liquid crystal element film was produced as an activeliquid crystal element film. As a base film of the liquid crystalelement film, two PC (polycarbonate) films (coefficient of thermalexpansion: 80 ppm/K, elongation at break: about 14.5%) in which an ITO(indium tin oxide) electrode layer was formed on one side were used. Onthe ITO electrode layer of one PC film of the two PC films, an LLC(lyotropic liquid crystal) coating layer and a liquid crystal alignmentfilm were sequentially formed. Here, the LLC coating layer was formedusing a known lyotropic liquid crystal compound (MCC, LB012). Thelyotropic liquid crystal compound was coated on the ITO electrode layerby a bar coating method and oriented by applying shear force to form anLLC coating layer. A known liquid crystal alignment film was formed onthe formed LLC coating layer. A liquid crystal alignment film was formeddirectly on the ITO electrode layer of the other PC film without formingan LLC coating layer. In a state where the two PC films were disposedopposite to each other so as to maintain a cell gap of about 12 μm orso, the liquid crystal element film was produced by injecting a mixture(MAT-16-1235 from Merck) of a liquid crystal host and a dichroic dyeguest therebetween and sealing the frame with a sealant. The opposedarrangement of the PC films was subjected such that the side on whichthe alignment film was formed faced each other. The liquid crystal layerof the active liquid crystal element film could be in a horizontallyoriented state when a voltage was not applied and could be switched to avertically oriented state by voltage application. In addition, here,when the liquid crystal layer of the active liquid crystal element filmwas in a horizontally oriented state, the optical axis and theorientation axis of the LLC coating layer were perpendicular to eachother. Subsequently, an optical device was produced by laminating aglass substrate having a thickness of about 3 mm, an adhesive film, theactive liquid crystal element film, an adhesive film and a glasssubstrate having a thickness of about 3 mm as well in theabove-mentioned order to produce a laminate, performing an autoclaveprocess at a temperature of about 100° C. and a pressure of about 2atmospheres, and encapsulating the active liquid crystal element filmbetween the outer substrates by the adhesive film. As the adhesive film,a TPU (thermoplastic polyurethane) adhesive film (thickness: about 4 mm)having the trade name A4700 from Covestro was used. The dynamic frictioncoefficient between the surface of the PC film of the active liquidcrystal element film and the TPU adhesive film was about 6.1.

Example 2

An optical device was produced in the same manner as in Example 1,except that the surface of the PC film contacting the TPU adhesive filmwas polished with a sandpaper to adjust so that the friction coefficientbetween the surface of the PC film and the TPU adhesive film was about2.3.

Test Example

The durability was evaluated by a method of evaluating the transmittancecharacteristics after maintaining each of the produced optical devicesat 100° C. for 7 days. As a result of the durability evaluation, it wasconfirmed that the optical characteristics described in Table 1 belowwere maintained before and after the maintenance at 100° C. for 7 days,and thus it had excellent durability. In addition, Table 1 below is theresults of measuring transmittance and haze (reference wavelength: about550 nm) of the optical devices in Examples 1 and 2. The transmittance orlike was evaluated by an ISO 13468 method using an NDH5000 instrument.It can be confirmed from Table 1 below that the optical device of thepresent application exhibits appropriate variable transmittancecharacteristics.

TABLE 1 Transmittance Haze Example 1 Example 2 Example 1 Example 2Applied  0 V 2.6% 2.5% 6.8% 7.1% Voltage 20 V 26.3% 27.3% 2.6% 1.6%

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

-   -   10: active liquid crystal element film    -   101: first portion    -   102: second portion    -   A, AA: folded area    -   D: bisector of the first portion    -   T: tangent of the bisector of the first portion    -   P: normal to the tangent of the bisector of the first portion    -   1022: line for measuring the angle of the second portion    -   20: polarizer    -   201: polarizing coating layer    -   30: outer substrate    -   40: adhesive film    -   50: buffer layer    -   110: base film    -   120: active liquid crystal layer

1. An optical device comprising: an active liquid crystal element film,wherein the active liquid crystal element film comprises: two basefilms; an active liquid crystal layer which is present between the twobase films, wherein the active liquid crystal layer contains a liquidcrystal compound and is capable of switching between a first orientedstate and a second oriented state; and a polarizing coating layer,wherein the polarizing coating layer is present between one of the twobase films and the active liquid crystal layer.
 2. The optical deviceaccording to claim 1, further comprising: a conductive layer is formedbetween one of the two base films and the polarizing coating layer; andan alignment film disposed between the polarizing coating layer and theactive liquid crystal layer.
 3. The optical device according to claim 1,wherein the polarizing coating layer comprises lyotropic liquidcrystals.
 4. The optical device according to claim 1, wherein thepolarizing coating layer comprises reactive mesogens and a dichroic dye.5. The optical device according to claim 1, wherein an angle formed byan average optical axis of the active liquid crystal layer in the firstoriented state and the light absorption axis of the polarizing coatinglayer is in a range of 80 degrees to 100 degrees or in a range of 35degrees to 55 degrees.
 6. The optical device according to claim 1,wherein the two base films have a coefficient of thermal expansion of100 ppm/K or less.
 7. The optical device according to claim 1, whereinan alignment film is disposed on each of the two base films, and anangle formed by alignment directions of the alignment films is in arange of −10 degrees to 10 degrees, in a range of 80 degrees to 100degrees, or in a range of about 160 degrees to 200 degrees.
 8. Theoptical device according to claim 7, wherein an angle formed by thealignment direction of the alignment film disposed on the one of the twobase films closest to the polarizing coating layer and the lightabsorption axis of the polarizing coating layer is in a range of 80degrees to 100 degrees.
 9. The optical device according to claim 1,wherein the active liquid crystal element film is a folded film.
 10. Theoptical device according to claim 1, further comprising: two outersubstrates, wherein the active liquid crystal element film is presentbetween the two outer substrates.
 11. The optical device according toclaim 10, further comprising: an adhesive film, wherein the activeliquid crystal element film is encapsulated by the adhesive film, andwherein the adhesive film is present between the two outer substratesand the active liquid crystal element film and on sides of the activeliquid crystal element film.
 12. The optical device according to claim11, wherein a surface of the active liquid crystal element film incontact with the adhesive film has a friction coefficient of 5 or lessagainst the adhesive film.
 13. The optical device according to claim 11,further comprising: a buffer layer disposed between the adhesive filmand the active liquid crystal element film, and having a Young's modulusof 1 MPa or less.
 14. The optical device according to claim 13, whereinthe buffer layer comprises an acrylate-based, urethane-based,rubber-based or silicone-based oligomer or polymer material.
 15. Anautomobile comprising: a body having one or more openings; and theoptical device of claim 1 attached to the one or more openings.